Generally, in sleep medical science, the sleeping stages of a sleeping person are divided into wakefulness/stages 1˜4Rapid Eye Movement (REM) sleep, and the quality of sleep of the sleeping person is evaluated through the analysis of the sleeping stages.
Currently, for technology for analyzing the sleeping stages of a sleeping person, [1] the analysis of sleeping stages using the frequency analysis of an electroencephalogram, [2] the analysis of sleeping stages using Heart Rate Variability (HRV), [3] the analysis of sleeping stages using oxygen saturation, and [4] the analysis of sleeping stages using an actigraph and an accelerometer are mainly used. Of the above-described methods, methods used for easily analyzing the sleeping stages at low cost are the methods [3] and [4].
[1] The method using an electroencephalogram considerably inconveniences a sleeping person because the sleeping person must sleep with electrodes attached to his or her head, and uses a high-priced brain wave amplifier, so that it is used only for special examination in a hospital.
[2] The method for measuring HRV also inconveniences a sleeping person in the case where electrodes are used. Furthermore, there is technology for detecting variation in heartbeat through non-restrictive electrocardiogram measurement using conductive fiber. However, in this technology, the skin of the sleeping person must come into close contact with the conductive fiber.
[3] The method using oxygen saturation also inconveniences a sleeping person because sensors must be attached to the sleeping person's fingers, ears and the like.
[4] The method using the wrist/waist type actigraph and an accelerometer cannot completely eliminate the inconvenience to patients because the accelerometer must be mounted on the wrist or the waist.
Meanwhile, in the case where weak sleeping stages 1˜2 do not proceed to strong sleeping stages 3˜4 due to snoring, insomnia or the like, it may be difficult to enjoy normal life due to drowsiness experienced during the daytime in daily life. In order to analyze such sleeping stages, electroencephalogram analysis using polysomnography, which is conducted in a hospital, must be carried out.
In the electroencephalogram analysis, the sleeping person's brain waves measured during sleep are divided according to frequency range, and the sleeping stages are determined based on the intensities in respective frequency ranges.
However, electroencephalogram analysis is performed by attaching electrodes to the head of a patient, so that it is difficult for the patient to sleep as usual due to the unfamiliar electrodes.
Movement that occurs during sleep is an important factor indicating whether a sleeping person has awoken. When movement occurs during sleep, the sleeping person is in a slightly awoken state or a completely awoken state. Accordingly, whether the sleeping person sleeps or is awake by analyzing the movement can be detected.
For the measurement of movement, a wristwatch type or waist attachment type movement detection device using an accelerometer has been developed. However, the wrist type/waist type detection device is problematic in that it may disturb the sleep of the sleeping person because inconvenience during sleep must be endured.
Furthermore, most existing sleep measurement devices are disadvantageous in that they cannot provide various sleep analysis signals.